Problem: If $a + b = 1$ and $x + y = 9$, what is $-8y - 8x - 10b - 10a$ ?
$= -10a - 10b - 8x - 8y$ $= (-10) \cdot (a + b) + (-8) \cdot (x + y)$ $= (-10) \cdot (1) + (-8) \cdot (9)$ $= -10 - 72$ $= -82$